1. Field of the Invention
The present invention relates to a sample cooling device for cooling a liquid sample to be analyzed in an analyzer for automatically analyzing the liquid sample, such as liquid chromatography, and a sampling apparatus provided with the sample cooling device.
2. Description of the Related Art
A sample rack (hereinafter simply referred to as a rack) for housing therein a plurality of sample containers containing a sample therein and placing them thereon is used in an automatic analyzer for automatically injecting a plurality of samples into a device and then analyzing them (see US 2012/0219473A1).
In an automatic analysis by, for example, liquid chromatography, when a rack housing therein a plurality of sample containers containing therein a small amount of sample is placed in a sampling apparatus, the sampling apparatus sequentially suctions the samples from the sample containers placed on the rack so as to inject them onto an analysis channel of the liquid chromatography according to a preset analysis program. The samples injected into the analysis channel are introduced into an analysis column in a mobile phase where the samples are separated according to components, and then, they are introduced to a detector disposed downstream of the analysis column, to be then detected.
A sample container that contains a sample waiting for an analysis out of the sample containers housed in the rack is generally left at room temperature. Some samples that are put must be kept at low temperature in order to prevent their degradation. In such a case, a sample cooling device is adapted to cool the sample container housed in the rack.
The sample cooling devices are classified into two types: a direct cooling type and an air cooling type. In a direct cooling type, a rack is made of metal having an excellent heat conductivity, and further, a cooler such as a Peltier device is brought into close contact with the bottom of the rack so as to adjust the temperature of a sample. In contrast, in an air cooling type, essential parts of a sampling apparatus including a rack are surrounded by a heat insulating case, and then, air inside of the case is cooled so as to adjust the temperature of a sample. The present invention relates to a sample cooling device of a direct cooling type.
FIG. 5 shows one example of a configuration of a sample cooling device of a direct cooling type in the prior art.
A Peltier device 2 serving as a cooler is fixed to a heat insulator 10. A heat conducting member 6 serving as a plate-like member having a heat conductivity is attached to the cooling surface of the Peltier device 2. The heat conducting member 6 is uniformly cooled by the Peltier device 2. A heat radiating fin 4 is secured to the heat radiating surface of the Peltier device 2, opposite to the cooling surface thereof, so as to allow heat absorbed from the heat conducting member 6 to radiate.
A rack 14 is placed on the heat conducting member 6. The rack 14 is constituted of a base 14a at the lower portion thereof and a cover 14b at the upper portion thereof. The base 14a is made of a material having an excellent heat conductivity such as aluminum whereas the cover 14b is made of a resin. The bottom surface of the base 14a is brought into direct contact with the surface of the heat conducting member 6, and further, the base 14a is cooled to a predetermined temperature by heat (cold heat) transmitted from the Peltier device 2 via the heat conducting member 6.
The rack 14 is provided with a plurality of concave portions for holding sample containers 16, respectively, each of which contains a liquid sample therein. The sample containers 16 housed in the concave portions, respectively, are cooled to a predetermined temperature by the Peltier device 2 via the base 14a and the heat conducting member 6. The cover 14b made of the resin is provided for keeping the coolness of the sample containers 16 that have been cooled by the base 14a. 
The sample cooling device of the direct cooling type shown in FIG. 5 has an advantage: it has a high heat conductivity, and therefore, it can be cooled down to the predetermined temperature in a short period of time, so that the temperature of the plurality of sample containers 16 housed in the rack 14 can be uniformly controlled. On the other hand, there arises a problem that moisture in the atmosphere during a cooling process is condensed on the sample containers 16, the base 14a of the rack 14, or the heat conducting member 6, thereby producing condensed water. When the rack 14 or the sample container 16, to which the condensed water adheres, is moved, the condensed water drops to dirty the surroundings or produces rust or mold. In view of this, it is inconvenient to treat the rack 14 or the sample container 16.
A sampling apparatus adopting the sample cooling device of the direct cooling type has taken the measures against the above-described problem by surrounding a space including the heat conducting member 6 and the rack 14 via a casing so as to provide a closed space isolated from the outside air, and further, housing a Peltier device for removing moisture inside of the casing so as to reduce the moisture inside of the casing. However, the outside air enters the casing when the rack 14 is put in or taken out, or a liquid tank of a needle cleansing liquid is housed inside of the casing, and therefore, it is markedly difficult to completely prevent the condensation in the rack 14 or the heat conducting member 6.
In view of the above, the condensed water always stays between the rack 14 and the heat conducting member 6 in the conventional sample cooling device, and therefore, the condensed water cannot be removed unless an analyzing person wipes it off.